a) How long will the energy in a 1470-kJ(350-kcal) cup of yogurt last in a woman doing work at t

step 1 Okay, to find how long it's going to take this woman to burn off her yogurt, we're going to use

A) How long will the energy in a 1470-kJ(350-kcal) cup of...

a) How long will the energy in a $1470-\mathrm{kJ}(350-\mathrm{kcal})$ cup of yogurt last in a woman doing work at the rate of $150 \mathrm{W}$ with an efficiency of $20.0 \%$ (such as in leisurely climbing stairs)? (b) Does the time found in part (a) imply that it is easy to consume more food energy than you can reasonably expect to work off with exercise?

a) How long will the energy in a $1470-\mathrm{kJ}(350-\mathrm{kcal})$ cup of yogurt last in a woman doing work at the rate of $150 \mathrm{W}$ with an efficiency of $20.0 \%$ (such as in leisurely climbing stairs)?
(b) Does the time found in part (a) imply that it is easy to consume more food energy than you can reasonably expect to work off with exercise?

Key Concepts

Energy Conversion

This concept involves translating energy between different units, such as converting the energy content of food from kilojoules or kilocalories into the joules used in physics calculations. Understanding this conversion is essential in contexts that compare food energy with mechanical work.

Power and Work

Power is defined as the rate at which work is performed or energy is transferred. In this context, work is the energy used for physical activity. Recognizing the relationship between power (energy per unit time) and total work helps explain how long a given energy supply lasts during exercise.

Efficiency

Efficiency in energy conversion describes the fraction of input energy that is successfully converted into useful work, with the remainder typically lost as heat. This concept is crucial when analyzing how biological systems, such as the human body, use food energy during physical activity.

Energy Balance

Energy balance refers to the relationship between energy intake, like food consumption, and energy expenditure through activities such as exercise. This concept underscores the difficulty of offsetting high caloric intake with realistic levels of physical activity, emphasizing that it is often easier to consume than to burn off excess energy.

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